Nowadays light emitting diode (LED) display panels are packaged mainly by using frit. FIG. 1 is a schematic diagram of a packaging scheme in the prior art in which a first substrate 1 and a second substrate 2 with a light emitting unit 4 arranged thereon are packaged together by a sealing material 3 (for example, frit). The sealing material 3 in solid state is melt by the irradiation of a laser 7 during the process of the packaging, and the first substrate 1 and the second substrate 2 are packaged together after the sealing material 3 is cured again.
The laser can only irradiate a part of sealing material 3 at a time, and stress release will occur between the first substrate 1 and the second substrate 2 when a part of the sealing material 3 is melted. The released stress may separate the first substrate 1 and the second substrate 2, and thus the first substrate 1 and the second substrate 2 cannot be effectively packaged by the sealing material 3, resulting in a problem of poor packaging.
Aiming at the above problem, a solution in the prior art comprises providing a thermal expansion layer and other interposed layer(s) on the outside (the side facing away from the second substrate 2) of the first substrate 1. When the sealing material 3 is irradiated by the laser and melted, the generated heat is also transferred to the thermal expansion layer and the thermal expansion layer is thus expanded, thereby pressing the first substrate 1 against the second substrate 2, which prevents the separation between the first substrate 1 and the second substrate 2 due to stress release. However, this solution needs to keep the laser irradiating from bottom to top (i.e., irradiating in a direction from the second substrate 2 to the first substrate 1), which makes the operation inconvenient. Furthermore, the thermal expansion layer is usually made of organic polymer material or elastic rubber and is apt to cause environmental pollution.
Another solution in the prior art comprises adding a clamping plate component on the outsides of both the first substrate 1 and the second substrate 2 so as to apply a clamping force to the first substrate 1 and the second substrate 2, and meanwhile providing a sensor to sense the pressure between the first substrate 1 and the second substrate 2 so as to avoid poor sealing effect due to weak clamping or device damage due to overclamping, thereby improving packaging quality. However, it is very difficult for the sensor to effectively sense the pressure between the first substrate 1 and the second substrate 2 during packaging in this solution because the distance between the first substrate 1 and the second substrate 2 is very small (generally, below 20 μm). Moreover, the effective integration of the sensor and the two substrates is also a difficult problem.